Inertial motion units (IMUs) are used to perform measurements of waves in water covered by landfast ice close to the ice edge in Svalbard. The effective noise level of the instruments is assessed in controlled wave tank experiments. A set of measurements collected in Tempelfjorden, Svalbard in March 2015 is presented, and the ability of the sensors to operate in the field is validated. Several characteristics of the recorded signals, including correlation between the different sensors, are analyzed. Horizontal and vertical motions are of the same order of magnitude. A clear transition in the signal properties is observed in relation with changes in incoming wave field and the development of cracks in the ice layer. We show that complex physics takes place when waves propagate in landfast ice and that the use of times series containing information on the full three-dimensional linear acceleration, rather than spectra, is required to capture the underlying phenomena.